The Netherlands expelled four "Russian agents" after the attempt and said the operation was carried out by Russia's GRU military intelligence agency, officials said.
Dutch intelligence thwarted a Russian cyber attack targeting the global chemical weapons watchdog in April and expelled four Russian agents, the government said on Thursday.
The Russians set up a car full of electronic equipment in the car park of a hotel next to the Organisation for the Prohibition for Chemical Weapons in The Hague in a bid to hack into its computer system, it said.
"The Dutch government finds the involvement of these intelligence operatives extremely worrisome," Dutch Defence Minister Ank Bijleveld told a news conference.
"Normally we don't reveal this type of counter-intelligence operation."
TRT World's Sarah Morice reports.
The Netherlands publicly identified the alleged Russian agents and said the operation was carried out by Russia's GRU military intelligence agency, Dutch officials said.
Britain helped the Netherlands with the operation, they added.
A laptop belonging to one of the four was linked to Brazil, Switzerland and Malaysia. The activities in Malaysia were related to the investigation into the 2014 shooting down of flight MH17 over Ukraine, Bijleveld added.
TRT World spoke to Lucy Taylor in Moscow for more details.
At the time of the attack the OPCW was investigating the nerve agent poisoning of former Russian spy Sergei Skripal and his daughter in Salisbury, England.
Dutch officials said it was not clear if the cyber operation was linked to that.
The head of the Dutch MIVD intelligence service, Major-General Onno Eichelsheim, told the news conference that the men travelled to Amsterdam's Schiphol Airport on April 4, on Russian diplomatic passports.
An official from the Russian embassy escorted them to The Hague, he said.
On April 11, they then hired a Citroen C3 and scouted the area around the OPCW — all the time being watched by Dutch intelligence.
"They were trying to commit a close access hack operation," he said.
'Clearly not on holiday'
The Russians set up in the Marriott Hotel next door to the OPCW and took photos, while parking the car at the hotel with the boot facing the OPCW, he said.
In the boot was electronic equipment to intercept the OPCW's Wi-Fi as well as login codes at the organisation, with the antenna hidden in the back of the car facing the OPCW.
"We intercepted it and expelled the four men from the country. It was a successful operation."
The Dutch spy chief said the Russians had originally taken a taxi from a GRU base in Moscow to the airport, and some of their mobile phones were activated in Moscow near the agency's headquarters.
When leaving The Hague, the men took all the rubbish from their room in a further bid to cover their tracks.
"They were clearly not here on holiday," said Eichelsheim.
News of the Dutch operation came a day after Britain and Australia blamed the GRU for some of the biggest cyber attacks of recent years — including one on the Democratic National Committee during the 2016 US presidential campaign.
They said the Russian military intelligence service could have only been conducting operations of such scale on Kremlin orders.
Russian President Vladimir Putin has repeatedly and angrily rejected similar charges. He told US President Donald Trump during a July summit in Helsinki that talk of Russia meddling in the 2016 election was "nonsense."
Moscow accuses West of 'spy mania'
Moscow accused the West of "spy mania" after Dutch security services said they had thwarted a Russian cyber attack on the OPCW.
"Western spy mania is gathering pace," a Russian foreign ministry representative told AFP.
Russia must stop cyber attacks on West — NATO
NATO's chief vowed on Thursday to strengthen the alliance's defences against attacks on computer networks that Britain said are directed by Russian military intelligence, also calling on Russia to stop its "reckless" behaviour.
"Russia must stop its reckless pattern of behaviour, including the use of force against its neighbours, attempted interference in election processes, and widespread disinformation campaigns," NATO Secretary-General Jens Stoltenberg said in a statement after Britain and the Netherlands said they had evidence of Russian cyber attacks.
"NATO will continue to strengthen its defence and deterrence to deal with hybrid threats, including in the cyber domain," he added as NATO defence ministers met to discuss new offensive cyber capabilities.
UK, Australia blame Russian military
Britain and Australia on Thursday blamed Russia's military intelligence service for some of the biggest cyber attacks of recent years — including one on the Democratic National Committee during the 2016 US presidential campaign.
They said the GRU military intelligence service could have only been conducting operations of such scale on Kremlin orders.
Britain's National Cyber Security Centre (NCSC) and the Australian government pointed the blame directly at alleged GRU front operations such as Fancy Bear and APT 28.
The announcement could further strain relations between Russia and Britain that began to deteriorate with the 2006 assassination of former Russian spy Alexander Litvinenko with polonium in London.
"This is not the actions of a great power; this is the actions of a pariah state," British Defence Secretary Gavin Williamson said during a visit to Brussels.
"We'll continue working with allies to isolate, make them understand they cannot continue to conduct themselves in such a way."
The Australian government added that Russia's actions violated its international commitments to "responsible state behaviour" in cyberspace.
"Cyberspace is not the Wild West," Prime Minister Scott Morrison and Foreign Minister Marise Payne said in a joint statement.